linux-kernel - Re: [PATCH] mm/filemap: do not allocate cache pages beyond end of file at read

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Message-ID: <20191028125702.xdfbs7rqhm3wer5t@box>
Date:   Mon, 28 Oct 2019 15:57:02 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Johannes Weiner <hannes@...xchg.org>,
        Steven Whitehouse <swhiteho@...hat.com>
Subject: Re: [PATCH] mm/filemap: do not allocate cache pages beyond end of
 file at read

On Mon, Oct 28, 2019 at 01:47:16PM +0100, Linus Torvalds wrote:
> On Mon, Oct 28, 2019 at 1:42 PM Kirill A. Shutemov <kirill@...temov.name> wrote:
> >
> > I've tried something of this sort back in 2013:
> >
> > http://lore.kernel.org/r/1377099441-2224-1-git-send-email-kirill.shutemov@linux.intel.com
> >
> > and I've got push back.
> >
> > Apparently, some filesystems may not have valid i_size before >readpage().
> > Not sure if it's still the case...
> 
> Well, I agree that there might be some network filesystem that might
> have inode sizes that are stale, but if that's the case then I don't
> think your previous patch works either.
> 
> It too will avoid the readpage() if the read position is beyond i_size.
> 
> No?

Yes. That's the reason the patch was rejected back then.

My point is that we need to make sure that this patch not break anything.

-- 
 Kirill A. Shutemov